High-pressure synthesis of rGO/TiO2 and rGO/TiO2/Cu catalysts for efficient CO2 reduction under solar light

•A one-pot method to synthesize TiO2-based catalysts in supercritical CO2 is reported.•These photocatalysts were used in CO2 photoreduction with simulated sunlight.•The best results were obtained with rGO50/TiO250 and rGO49.5/TiO249.5/Cu1.•CH4 production rate was 1.7 times higher than the best obtained with Cu/TiO2 NPs. [Display omitted] This work reports the synthesis of rGO/TiO2/Cu and rGO/TiO2 nanocomposites to obtain methane and CO from CO2 photoreduction with water vapour and simulated solar light. A novel, facile and efficient one-pot method is proposed to directly synthesize the composites in supercritical CO2-ethanol medium. The influence of wt% rGO on both their physicochemical properties and photocatalytic activity have been studied. The most striking changes observed have been their large increase in the visible range absorbance and absorption thresholds as compared to commercial TiO2, both effects increasing with the amount of rGO. These findings later resulted in an improved electron charge transfer and a better photocatalytic activity of the composite catalysts with higher rGO content. Nevertheless, the best catalytic performance (7.4 µmol CO2/g TiO2·h conversion rate) was achieved when the binary rGO/TiO2 nanocomposite was doped with metallic Cu at 1 wt%, due to its better electron/hole separation as compared to rGO-TiO2.